The present disclosure relates to, in various exemplary embodiments, processes in synthesizing a branched amorphous polyester resin with a target glass transition temperature (Tg). The branched amorphous polyester resin of the present embodiments may be used in toners, such as Emulsion Aggregation (EA) toners, which are prepared using an emulsion aggregation process. Emulsion aggregation processes for the preparation of toners are illustrated in a number of Xerox patents, the disclosures of which are totally incorporated herein by reference, such as U.S. Pat. Nos. 5,290,654, 5,278,020, 5,308,734, 5,346,797, 5,370,963, 5,344,738, 5,403,693, 5,418,108, and 5,364,729.
Toners must not aggregate or block during manufacturing, transport or storage periods before use in electrographic systems, and must exhibit low fusing temperature properties in order to minimize fuser energy requirements. Accordingly, to satisfy blocking requirements, toner resins should exhibit a Tg of from about 40° C. to about 80° C. If the Tg exceeds 60° C., then it may lead to issues of long aggregation time in the toner producing process, and elevated minimum fix temperature for the toner to adhere properly to the substrate. The minimum fixed temperature is the minimum temperature needed for the toner particles to adhere to the substrate.
Fixing performance of toners can be characterized as a function of temperature and pressure. The temperature at which the toner adheres to the fuser roll is called the hot offset temperature (HOT). When the fuser temperature exceeds HOT, some of the molten toner adheres to the fuser roll during fixing and is transferred to subsequent substrates containing developed images, resulting for example in blurred images. This undesirable phenomenon is called offsetting. Less than the HOT of the toner is the minimum fixing temperature (MFT) of the toner, which is the minimum temperature at which acceptable adhesion of the toner to the support medium occurs. Toner resins should exhibit a MFT of 60° C. or above (e.g., from about 60° C. to about 140° C.) to adhere properly to the substrate, and a HOT of 190° C. or above (e.g., from about 190 to about 230) to avoid print defects and fuser contamination.
One major difficulty in producing branched amorphous polyester resins is to properly control the degree of branching which is the fraction of the resin that is not completely soluble in solvent. The controlled amount of branching is necessary to optimize the fusing performance. In general, typical concerns with the synthesis of branched amorphous polyester resins include the uses of dangerous materials, such as, ethylene oxide, and propylene oxide, which are dangerous flammable toxic gases that require special costly equipment for safe handling. Another concern with the existing process for producing branched amorphous polyesters is the isolation of the alkoxylated intermediates prior to use in the polyesterification step, which leads to additional cost and complexity in synthesizing the final branched amorphous polyester resins.
Thus, there exists a need to improve the current process of producing branched amorphous polyester resins while maintaining the desired target glass transition temperature of the resin.